Browse Prior Art Database

Cable Transport System

IP.com Disclosure Number: IPCOM000088265D
Original Publication Date: 1977-May-01
Included in the Prior Art Database: 2005-Mar-04
Document File: 4 page(s) / 70K

Publishing Venue

IBM

Related People

Yosmali, K: AUTHOR

Abstract

The linear and reversible motion of an inertia load is provided simply with a cable transport system. It meets the requirements of low cost, quietness of operation, absence of backlash, speed ratios of 5-to-1 and more, minimum variation in friction loads, low friction loads, minimum parts, stiffness, minimum occupied space, reliability, serviceability, and versatility.

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Cable Transport System

The linear and reversible motion of an inertia load is provided simply with a cable transport system. It meets the requirements of low cost, quietness of operation, absence of backlash, speed ratios of 5-to-1 and more, minimum variation in friction loads, low friction loads, minimum parts, stiffness, minimum occupied space, reliability, serviceability, and versatility.

In Fig. 1, a pulley 10 and a cord drum 11 are used. Drum 11 is attached to the shaft of a motor 12. Angles (alpha) and (beta) of cables 17 and 17a are forned as the carrier load 14 moves to the left side, and these angles vanish when load 14 is at the right hand side.

This angular motion of cable 17 and 17a maintain correct threading of the cord drum grooves 18. Due to the space occupied by motor 12, the total machine width required is relatively large.

Fig. 2 shows another arrangement that minimizes total machine width. Cables 17 and 17a is biased by spring 19. Three pulleys 10, 15, and 16 and cord drum 11 are used. Again, drum 11 is attached to the shaft of motor 12. The distance (d) is long enough to have motor 12 located in the rear inside of a machine, and the angle (alpha) is small to allow correct threading of the cable over the grooves of the drum. The diameter of pulley 10 is larger than pulleys 15 and 16, and pulley 10 is positioned at a 45-degree inclination to maintain the cables parallel.

Wire cables with a normal operating load of 35 pounds should have a minimum of 0.8 inch pulley diameter. Therefore, the speed of the motor is limited by this minimum pulley diameter and by the required speed of the inertia load. If carrier speed is 5 inches per second, the motor runs at 100 rpm. At this speed a DC motor is inefficient and overheats. Motor speed control is difficult. However, a torque motor can be used in place of the DC servo motor shown in Fig. 2. A DC servo motor with speed reduction is equivalent to a DC torque motor except that the torque motor has a higher torque-to-inertia ratio, thus, faster response. Economics and performance requirements dictate the choice between the two motors. If the inertia load needs accurate position control, the DC motor is replaced with a stepper motor. Stepper motor control methods need to be developed in order to achieve a stable system.

Fig. 3 shows an arrangement with a no-backlash cable speed reducer, which enables efficient motor o...